Steering apparatus of a type where a steering wheel operable by a human driver is adjustable in position in a front-rear direction of a vehicle are commonly known. In one example of such steering apparatus, an outer column is supported by a bracket, and a cylindrical inner pipe is retained by the outer column for movement in the front-rear direction of the vehicle (i.e., in such a manner that it is movable in the front-rear direction of the vehicle), as disclosed in Japanese Patent Application Laid-Open Publication No. 2012-40949.
FIG. 8 hereof shows the steering apparatus 100 disclosed in the above-mentioned No. 2012-40949 publication. As shown in FIG. 8(a), the steering apparatus 100 includes; the outer column 103 supported by the bracket 101 and having a bolt 102 passed therethrough; the inner pipe 104 retained by the outer column 103 for movement in the front-rear direction (left-right direction in the figure); and an impact energy absorbing member 110 mounted on the upper surface of the inner pipe 104 for absorbing impact energy when an impact has been input from the steering wheel.
The impact energy absorbing member 110, which is formed by bending a metal plate, includes: a base section 111 fixed to the upper surface of the inner pipe 104; an upward projecting section 112 extending upward from the rear end of the base section 111; an upper plate section 113 extending rearward from the upper end of the upward projecting section 112; an abuttable section 114 projecting downward from the rear end of the upper plate section 113 and abuttable against the bolt 102; an energy absorbing section 115 extending forward from the lower end of the abuttable section 114 and constructed in such a manner that, when an impact has been input to the inner pipe 104, it absorbs impact energy while deforming by abutting against the inner pipe 104; and a front stopper 116 projecting upward from the front end of the energy absorbing section 115 for restricting rearward movement of the inner pipe 104.
Referring to FIG. 8(a) and FIG. 8(b) as well, the bracket 101, the bolt 102 and the outer column 103 are immovably fixed, while the inner pipe 104 and the impact energy absorbing member 110 are movable in the front-rear direction. By sliding the inner pipe 104 in the front-rear direction, the human driver can adjust the steering wheel to a desired position. Retaining force imparted by the outer column 103 to the inner pipe 104 can be increased as fastening force by the bolt 102 is increased. By the increased retaining force, the movement of the inner pipe 104 in the front-rear direction can be restricted.
The abuttable section 114 can be said to be a rear stopper for restricting forward movement of the inner pipe 104 in normal operating conditions. FIG. 8(b) shows the inner pipe 104 and the impact energy absorbing member 110 having moved to their respective forward movement limit positions.
If an impact load has been input from the rear to the steering apparatus 100 in the state shown in FIG. 8(a) and if the input impact load is large, the inner pipe 104 moves forward against the fastening force of the bolt 102, so that the abuttable section 114 abuts against bolt 102 as shown in FIG. 8(b). If the impact load is further input in this state, the inner pipe 104 further moves forward and thus the energy absorbing section 115 absorbs energy of the impact (impact energy) while deforming by abutting against the bolt 102, as shown in FIG. 8(c).
In such a steering apparatus 100 equipped with impact energy absorbing performance or function, it is desirable that constant impact absorbing characteristics be achieved stably. In other words, it is desirable that constant impact absorbing characteristics be achievable stably per product (per steering apparatus).
However, the manner in which the energy absorbing section 115 abuts against the inner pipe 104 would vary per product. In the steering apparatus 100, the energy absorbing section 115 moves while contacting the upper surface of the inner pipe 104. Thus, it is supposed that impact energy absorbing characteristics of the energy absorbing section 115 are influenced by friction between the inner pipe 104 and the energy absorbing section 115. Due to the variation in the manner in which the energy absorbing section 115 abuts against the inner pipe 104, the impact energy absorbing characteristics would differ per different product.